In a healthcare facility it is necessary that all equipment and materials used for treating patients are safe for use; the chance of spreading infection should be minimal. As is well known, articles used in the operating room, such as surgical instruments, must be sterilised before each use.
The current steam sterilization industry best practice packaging using porous materials has a contestable and identified risk associated for the patient, by transference of infection and the risk of re-contamination of the sterilized items from airborne micro-organisms.
Currently used medical packaging (with the exception of irradiation methods) typically requires a porous section to facilitate the removal of air and the introduction and removal of sterilant and moisture. This porous section is then relied on as the barrier after processing. Variations in temperature and pressure can result in air being drawn into the sterilised article with the potential for recontamination.
Not withstanding the substantial research and investment in breathable sterile barrier systems the necessity of the barrier material to be breathable during the sterilisation process/cycle in the steriliser chamber and then conversely an impervious barrier system after sterilisation is extremely unlikely. This conflicting demand of the breathable barrier system poses a dilemma for most current products.
The dichotomy of the sterile barrier system persists in current practices and the challenge for the packaging suppliers and users is that the sterile barrier system must be porous or breathable to facilitate air removal and sterilant penetration/removal during the sterilisation process within the steriliser and then crucially at the completion of a successful sterilisation process, provide impervious protection as a viral and liquid barrier until aseptic release at point of use.
In current practice at the end of a correct sterilisation process, articles inside the steriliser chamber are sterile. The air in the room where the steriliser is installed contains dust particles, which may carry microorganisms; therefore the potential exists when taking out the load from the steriliser that it may be contaminated again.
Additionally sterile articles are usually stored for quite some time before use and moreover they are transported through the healthcare facility to the place they are to be used. It is thus obvious that when not protected the goods may be re-contaminated by the time they are used.
Articles therefore must be placed in a packaging to prevent recontamination after sterilisation and at the same time the packaging should be suitable to allow sterilisation of the articles it contains within a steriliser chamber. Packaging is essential for maintaining sterility; moreover the packaging must protect its load against damage during handling and transport.
Current practices of packaging depending on the use, storage and transportation, dictates that a sterile article should be packaged in one or more packaging layers. The inner primary packaging endeavors to prevent recontamination of the articles after sterilisation and hopes to provide an effective microbial barrier whilst it must allow the passage of air and the sterilant. The secondary layer is applied to facilitate proper storage and transport protection of the articles whilst it must allow the passage of air and the sterilant and in addition the combination of the packaging layers must allow the passage of air and the sterilant. The ‘barrier’ to microbiologic ingress is thus defined as a tortuous path.
The combination of the packaging layers therefore strives to function as a sterile barrier system that enables medical articles to be sterilised, maintain sterility and ensure the articles sterility until the time of use or the packaging expiry date. The ISO definition of a sterile barrier system is “a minimum package that prevents ingress of micro-organisms and allows aseptic presentation of the product at the point of use”.
Due to current sterilisation practices the sterile barrier system is required to be “breathable” and sterile packaging is the single biggest challenge to successful sterilisation. Due to the requirement of the packaging to act as a barrier once sterile—it is inherently difficult to extract air, insert steam and subsequently extract the resultant condensate to leave the load dry, through this barrier system. Advances in non-woven wraps with their more effective barrier construction have contributed to compounding this problem.
Fundamental to air extraction is the rate at which the air to be removed from the pack can physically pass through the barrier. No allowance for load sizing or service (water pressure/steam supply) variance or time-based extraction is implemented. A common problem with today's sterilisers is the vacuum system is too efficient and the vacuum stages cycle faster than the air can get out through the barrier (A common symptom of this is packs ‘blowing up’ under vacuum). Conversely the pressure stages that are supposed to force steam into the packs are also too efficient and the steam simply cannot penetrate effectively in the time allowed due to the multiple layers (torturous path) of the porous wrap.
This very typical problem encountered with breathable sterile barrier systems is made even worse by lightly loaded cycles or mixed loads where some porous packs are in with non-porous instrument cases etc. and results in inadequate air removal, steam penetration failure and non-sterile packs within the loads.
Traditionally packaging materials were reusable but due to their inadequate microbial barrier properties most of these traditional materials do not meet the requirements for primary sterile packaging anymore. Presently non-wovens, laminated film pouches, paper bags and containers are used as primary packaging materials. These include muslin wraps, various paper wraps and non-woven wraps, or alternatively laminated film pouches or sterilisation containers. The wraps are typically secured by autoclavable tape which may become detached during processing or in the handling of a package leading to rejection of the package. An important feature of fabric is its “breathability” or the ability of the fabric construction to allow the passage of air and water vapour (i.e. steam). Current practices where breathable packaging is required to allow the passage of the sterilant (water vapour/steam) in and out of the package during the sterilisation process places huge demands on the breathable packaging at the conclusion of the sterilisation process to then act as a viral and liquid barrier to ensure impervious protection of the terminally sterile load. The sterilised package should be constructed so that it may be easily opened without the packaging contaminating the contents.
The minimum requirement of any packaging configuration is that it will maintain sterility of the package load until aseptic presentation at the point of use.
Due to the many variables sterilisation services practitioners are faced with everyday new standards are evolving and the International Organisation for Standardisation (ISO) is working globally to coordinate standards.
The most recently published standard ANSI/AAMI ISO 11607:2008 section titled “Packaging for terminally sterilised medical devices” has two parts namely; Part1: Requirements for materials, sterile barrier systems and packaging systems, and Part2: Validation requirements for forming, sealing and assembly processes. The emphasis is clearly on patient safety regardless of where or how the product is sterilised.
Packaging utilized for sterilisation and forming a barrier system for subsequent storage and transportation is typically comprised of non-woven wraps, paper and plastic pouches or rigid metal and plastic vented containers.
Rigid containers offer another option for enabling sterilisation of medical instruments and items. They are usually re-usable and come in a variety of sizes and materials.
The containers consist of a receiving body, often with a perforated base, over which perforations a filter of porous material is fitted and located in place with a retainer. A separate lid, with a similar perforated area, filter and retainer is latched and locked onto the base. The lid has a silicon seal fitted around the top for sealing to the base. The items to be sterilised are typically loaded into a removable basket or tray that is lowered into the container.
Rigid containers being reusable are susceptible to damage over time and must be carefully inspected before each use. Correct placement of the filter is essential and the filter material must be of the manufacturers approved type.
Unfortunately this visual inspection methodology is very subjective and there is no qualitative way of determining the biological barrier integrity of the locked container post sterilisation in an autoclave. Small dents in the base or lid mating areas or nicks in the seal are likely to mean the seal is unable to form a barrier. Defects in or incorrect fitment of the filters and retainers can expose the perforations and provide a path for contamination. Clinicians therefore have less confidence in the efficacy of the container's sterile barrier and the sterility of the contents the older the container gets.
Re-use requires decontamination and proper cleaning of the containers and lids. This means additional resources for the hospital both in staffing and services such as steam, water and detergents.
Servicing of the containers is an ongoing and real cost including the requirement to purchase additional containers whilst damaged containers are off site for repair.
The applicant's prior application published as WO2007/055595 discloses a sterilisation method and apparatus in which items to be sterilised may be sterilised within a plastic bag whilst the exterior of the sterilisation bag is maintained at atmospheric pressure. The applicant's prior application WO2010/093265 discloses an improved bag. The disclosure of these applications is hereby incorporated by reference.
It is an object of the invention to provide an improved sterilisation container, system and apparatus or to at least provide the public with a useful choice.